Special purpose telecommunication systems are used to provide a variety of specialized services. One example of such a system is a cellular mobile telecommunication system, which provides the service of connecting mobile telecommunication customers each having a mobile unit to land-based customers who are served by the common carrier public telephone network. In such a system, all incoming and outgoing calls are routed through a mobile telecommunication switching office that is connected to a group of cell sites (radio stations) which communicate with mobile units.
One example of such a prior art special purpose telecommunication system is the Advanced Mobile Phone Service (AMPS) System described in The Bell System Technical Journal (BSTJ), V. 58, No. 1, Part 3, January 1979, pp. 1-270. The mobile units are served by radio stations or cell sites, each of which is located in one cell area of a larger region. Each cell site in the region is connected by a group of communication links to the mobile telecommunication switching office. Each cell site contains a group of radio transceivers (transmitter/receivers), and each transceiver is connected to one communication link. Each transceiver operates on a pair of frequencies, one frequency to transmit radio signals to the mobile unit, the other frequency to receive radio signals from the mobile unit.
The first stage of a communication connection is set up when a transceiver in a cell site, operating at a given frequency pair, is turned on and a mobile unit is tuned to the same frequency pair. The second stage of the communication connection is between the communication link connected to this transceiver and the common carrier public telephone network. This second stage of the communication connection is set up in the mobile telecommunication switching office, which is connected to the common carrier public telephone network by incoming and outgoing trunks. The mobile telecommunication switching office contains a switching network to switch a mobile customer's speech signals from the communication link to an incoming or outgoing trunk.
The mobile telecommunication system is controlled by a mobile telecommunication controller at the mobile telecommunication switching office and a cell site controller at each cell site associated with the mobile telecommunication switching office. A plurality of data links connect the mobile telecommunication controller and the associated cell site controllers. The mobile telecommunication controller under control of complex software controls the switching network. The mobile telecommunication controller also controls the actions of the associated cell site controllers by generating and interpreting the control messages that are exchanged with the associated cell site controllers over the data links. The cell site controllers at each cell site, in response to control messages from the mobile telecommunication controller, control the transceivers at the site. The control processors at each cell site also control the tuning of mobile units.
With today's rapidly moving technology, new and more efficient designs of telecommunication switching systems and processors are continually being evolved and the demand for new specialized business communication services is ever increasing. Prior art cellular mobile telecommunication switching system designs suffer from inflexibility and are difficult to adapt to the use of new, more cost-effective technologies and the offering of new specialized services. For example, to incorporate a new telecommunication switch into an existing cellular mobile telecommunication switching system design, or to adapt this system to offer a new kind of business communication service, usually requires a major design effort. Complex new control software must be designed and/or new interface hardware may be required between the mobile telecommunication controller and the units controlled by that controller.
An advance in the cellular mobile telecommunication field is disclosed in U.S. Pat. No. 4,599,490, wherein a business communication system is used as the switch element in the mobile telecommunication switching ofice. This is a master-slave arrangement wherein the mobile telecommunication controller is used for controlling the communication link to incoming/outgoing trunk connections through the business communication system. The mobile telecommunication controller controls the operations of the radio transceivers, mobile units, and one end of the communication links connecting cell sites to the business communication switching system. The mobile telecommunication controller controls channel selection, paging, mobile alerting, and hand-off operations. A separate business communication system processor, in the business communication switching system, controls the setting up of a connection in a switching network between the incoming and outgoing trunks to the common carrier public telephone network and the communication links to the cell sites. A data link interconnects the mobile telecommunication controller and the business communication system processor. When the business communication system processor receives incoming mobile call data from the common carrier public telephone network, it sends identification data corresponding to the incoming identity code to the mobile telecommunication controller. The mobile telecommunication controller controls the setting up of a connection between a mobile unit corresponding to the identification data and a selected one of the communication links which connect the cell sites with the business communication switching system. The mobile telecommunication controller controls the remainder of the connection by sending the identification of the selected communication link to the business communication switching system, which sets up a connection between the selected cell site communication link and the incoming trunk from the common carrier public telephone network associated with the incoming call.
In this system, a small group of primitive commands is exchanged between the business communication switching system and the mobile telecommunication controller. Advantageously, the use of such primitive commands permits any modern program-controlled business communication switching system to be readily adapted to communicate in a standard way with and to be responsive to commands from the mobile telecommunication controller. Thus, different business communication system processors and mobile telecommunication controllers, each controlling their own associated equipment, can easily be interconnected. For example, using this arrangement, a complete mobile telecommunication system can be formed using a standard mobile telecommunication controller and using any manufacturer's adapted modern program-controlled business communication switching system.